Mapping locations based on received signal strengths

Abstract

Disclosed is a system for updating an RSSI-based map. A scanning devices notes which tags are seen during a scan and measures a “proxy distance” from the scanning device to each tag. When the scan is initiated, the scanning device measures the RSSIs from the local WAPs. The current location of the scanning device is determined by triangulating from the proxy distances of the scanned tags. That location is then correlated with the contemporaneously measured RSSIs. The correlation is used to update the RSSI-based map. In some embodiments, it is not the scanning device that measures the RSSIs. Instead, the WAPs measure the RSSIs from the scanning device whenever the scanning device transmits the results of a scan. In some embodiments, the operator of the mapped environment places scannable tags at fixed locations. Scans of these fixed-location tags are especially useful when determining the current location of the scanning device.

1 . A scanning device comprising:
 a scan transceiver configured for transmitting a scan and for receiving results of the scan, the results comprising a list of one or more tags found by the scan;   a communications transceiver configured for communicating with a plurality of wireless access points (WAPs); and   a processor operatively coupled to the scan transceiver and to the communications transceiver, the processor configured for:
 analyzing, for at least some of the tags found by the scan, proxy distances between each tag and the scanning device; 
 analyzing received signal strength indications (RSSIs) from signals received, via the communications transceiver, from at least some of the WAPs; and 
 transmitting, via the communications transceiver to a map server remote from the scanning device, at least some of the scanned-tag proxy distances and the WAP RSSIs. 
   
     
     
         2 . The scanning device of  claim 1  wherein the scanning device is selected from the group consisting of: an RFID scanner and a laser scanner. 
     
     
         3 . The scanning device of  claim 1  wherein at least some of the tags found by the scan are associated with fixed locations. 
     
     
         4 . The scanning device of  claim 1  wherein the communications transceiver is a WiFi transceiver. 
     
     
         5 . The scanning device of  claim 1  wherein the proxy distance for a tag found by the scan is based, at least in part, on a selection from the group consisting of: a distance measured between the tag and the scanning device, a strength of a returned signal associated with the tag, and an indication of a lowest-power scan that found the tag. 
     
     
         6 . The scanning device of  claim 1  wherein the results of the scan and the reception of signals from the WAPs to be analyzed are received essentially simultaneously. 
     
     
         7 . The scanning device of  claim 1  wherein the processor is further configured for:
 filtering the list to remove tags, if any, whose proxy distances are above a threshold. 
 
     
     
         8 . The scanning device of  claim 1  wherein the processor is further configured for:
 filtering the list to remove tags, if any, that are not associated with fixed locations. 
 
     
     
         9 . The scanning device of  claim 1  further comprising:
 a user interface operatively coupled to the processor, the user interface configured for presenting an indication of a present location of the scanning device to a user of the scanning device; 
 wherein the processor is further configured for:
 transmitting, via the communications transceiver to the map server, a second set of WAP RSSIs; 
 receiving, via the communications transceiver from the map server, an indication of a location of the scanning device; and 
 presenting, via the user interface to the user of the scanning device, the location indication. 
 
 
     
     
         10 . A map server comprising:
 a communications transceiver configured for communicating with a wireless access point (WAP); and   a processor operatively coupled to the communications transceiver, the processor configured for:
 receiving, via the communications transceiver from a scanning device remote from the map server, proxy distances from scanned tags; 
 receiving, via the communications transceiver, WAP RSSIs; 
 analyzing at least some of the scanned-tag proxy distances to determine a location of the scanning device; and 
 storing, in a non-transitory computer-readable memory, a map correlating the determined location with at least some of the WAP RSSIs. 
   
     
     
         11 . The map server of  claim 10  wherein the WAP RSSIs are measured by the scanning device. 
     
     
         12 . The map server of  claim 10  wherein the WAP RSSIs are measured by one or more WAPs. 
     
     
         13 . The map server of  claim 10  wherein determining a location of the scanning device is based, at least in part, on fixed locations of the scanned tags as stored in a non-transitory computer-readable memory. 
     
     
         14 . The map server of  claim 10  wherein the processor is further configured for:
 filtering the proxy distances to remove tags, if any, whose proxy distances are above a threshold. 
 
     
     
         15 . The map server of  claim 10  wherein the processor is further configure for:
 filtering the proxy distances to remove tags, if any, that are not associated with fixed locations. 
 
     
     
         16 . The map server of  claim 10  wherein the processor is further configured for:
 receiving, via the communications transceiver, a second set of WAP RSSIs; 
 based, at least in part, on the stored map, determining a location corresponding to the second set of WAP RSSIs; and 
 transmitting, via the communications transceiver, an indication of the determined location.